Problem: Gabriela is 12 years younger than Ishaan. Twelve years ago, Ishaan was 3 times as old as Gabriela. How old is Ishaan now?
Answer: We can use the given information to write down two equations that describe the ages of Ishaan and Gabriela. Let Ishaan's current age be $i$ and Gabriela's current age be $g$ The information in the first sentence can be expressed in the following equation: $i = g + 12$ Twelve years ago, Ishaan was $i - 12$ years old, and Gabriela was $g - 12$ years old. The information in the second sentence can be expressed in the following equation: $i - 12 = 3(g - 12)$ Now we have two independent equations, and we can solve for our two unknowns. Because we are looking for $i$ , it might be easiest to solve our first equation for $g$ and substitute it into our second equation. Solving our first equation for $g$ , we get: $g = i - 12$ . Substituting this into our second equation, we get the equation: $i - 12 = 3($ $(i - 12)$ $ -$ $ 12)$ which combines the information about $i$ from both of our original equations. Simplifying the right side of this equation, we get: $i - 12 = 3i - 72$ Solving for $i$ , we get: $2 i = 60$ $i = 30$.